Help requested with css first-child problem

Hi, my name is Oliver, this is my first post, and I've only been using HubSpot for 2 months now. I want to say this forum is really helpful, a lot of really smart people on here. While I do have some HTML, CSS and JavaScript experience, I am by no means a developer.

I'm building out a template with a flexible column sidebar, and custom modules for each sidebar section. I've got them all good, except the video section. The problem I have is that the first iteration of a video should not have the grey top border. I had it working at one point with a certain layout of div's, span's etc. But the video links didn't work. So now I've got everything working except the first-child code. Here is a link to the page as it currently stands: http://westech-dev-4871855-4871855.hs-sites.com/rapisand-plus-treatment-for-high-solids-waters-1?hs_.... I have tried too many permutations of the css in question () to mention. Here is the css in it's original state:

@Pixelwerx, Good! I looked at your code in my inspector and your path didn't line up with the order of the elements. I have this nifty chrome extension called live editor that automatically applies any css you write to the page. I don't use it as often as you might think but it is great for these types of situations.

@Jsum - Just installed live editor, thanks for the tip, I think it will help when debugging psuedo selectors most since chrome inspector freaks out sometimes when you attempt to add a new style definition for :after and :before